As a molding method for optical parts such as lenses there has heretofore been known a method using liquid photocurable resin. However, in case of using liquid photocurable resin, there are problems such as it is difficult to maintain the film thickness constant, bubbles are mixed in the resin, and handling of the resin is troublesome. In view of these problems there has been proposed a lens molding method using a curable sheet composition (i.e., a sheet comprising a curable composition) (see JP 7-17132A).
In the conventional molding method using a curable sheet composition, an optical element pattern or the like is molded on a film or a film substrate. In this case, if direct molding is performed, that is, if a sheet is placed on a glass substrate and a female mold is pressed against the sheet to effect molding, problems related to durability have heretofore been encountered such as, for example, the sheet peels off from the glass surface when stripping the glass substrate-sheet combination from the female mold, which is due to poor adhesion of the sheet to the glass substrate, or peeling results from a long-term outdoor use.
On the other hand, as a direct molding method for a glass substrate there has been proposed such a method as is disclosed in JP 2006-231917A wherein a pasty curable composition is applied onto a female mold and then actinic light is radiated to the composition to cure the composition. In this conventional method, however, it is necessary to treat the glass substrate with a coupling agent in order to enhance the adhesion between the curable composition and the glass, resulting in increase in the number of steps. However, since the composition is pasty, there has been the problem that consideration must be given to the mixing of bubbles in the composition and treatment of a protruded portion.